A bid by two republicans to overturn a landmark civil ruling that found them responsible for the Omagh bomb has been rejected by the European Court of Human Rights.

Convicted Real IRA chief Michael McKevitt and Co Louth man Liam Campbell were two of four republicans ordered to pay £1.6 million in damages to bereaved relatives who took the historic case.

The Real IRA outrage in the Co Tyrone market town in August 1998 killed 29 people, including a woman pregnant with twins, and injured 200 others.

The pair took their case to Europe, arguing that the civil trial in Belfast High Court had been unfair.

They said the judge should have applied a criminal rather a civil standard of proof, due to the severity of the allegations, and further claimed that the evidence of an FBI agent heard during the trial should not have been admitted.

The seven ECHR judges unanimously rejected the case and made clear their decision was final.

"The applicants had not demonstrated that their trial was unfair, and the Court dismissed their applications," said an ECHR statement.

McKevitt was jailed for 20 years in August 2003 after being convicted of directing a terrorist organisation and being a member of the Real IRA.

The ECHR case was the latest in a series of separate legal attempts by the four defendants to overturn the 2009 civil judgment.

The relatives who took the action are still pursuing the damages.

No one has ever been criminally convicted of the bomb, which inflicted the most bloodshed of an single atrocity during the Northern Ireland Troubles.

One of the key witnesses in the families' case was FBI agent David Rupert, who had infiltrated the Real IRA.

He did not attend the trial in person due to concerns about his security and medical condition.

McKevitt and Campbell argued that their lawyers' inability to cross-examine Mr Rupert had been unfair.

The ECHR dismissed this argument, insisting the trial judge had taken the "appropriate safeguards and considerations" in dealing with the evidence of an absent witness.

The applicants also claimed the judge should have applied a criminal standard of proof - beyond reasonable doubt - rather than a civil one - balance of probabilities - due to the severity of the allegations facing them.

The European judges said that was not necessary because the proceedings had been for a civil claim for damages and there had been no criminal charge involved.

Rejecting both grounds for the application, the ECHR said: "The Court found that the national court's findings could not be said to have been arbitrary or unreasonable."

Michael Gallagher, whose son Aiden was killed in the bomb, described the ruling as "vindication" for the families.

"We feel like we have been under siege since the first judgment, with appeal after appeal," he said.

"We are relieved it is now over. The families have been vindicated.

"Enormous expense has been paid by taxpayers to make sure these people got the best of British and European justice. The British and Irish Governments must now make sure the interests of the victims comes first."

He said the authorities had to help the families recover the money owed to them.

"It would be a very hollow judgment if it was only words," he said.

"These people value money and it's where it can hurt them and both governments must work together to make sure the families receive the money that was awarded to them."

Mr Gallagher made clear the bereaved relatives would continue to campaign for a full cross-border inquiry into the Omagh bombing, amid persistent claims the outrage could have been prevented.

Diane Dodds, Democratic Unionist MEP, said it was unfair that the men had access to legal aid to fight their case in Europe and branded it an abuse of human rights laws.

"The reality is whilst these individuals had full access to legal aid during the appeal process, the families of those murdered in the Omagh bombing have not received a single penny from the civil ruling," she said.

"Everyone, Republican or otherwise has their own particular part to play. No part is too great or too small, no one is too old or too young to do something."

~Bobby Sands 1954-1981~

'Mother Erin'

Two divine persons in one. A mother lamenting her children in bondage. A girl ravished by the Saxon, who weeps over her stringless harp. But her young champions keep watch in the mountains, awaiting the dawn of the bright sun of Freedom. They will gather around her with pikes and swords.